WASHINGTON — Polar bear cubs forced to swim long distances with their mothers as their icy Arctic habitat melts appear to have a higher mortality rate than cubs that didn't have to swim as far, a new study reports.

Polar bears hunt, feed and give birth on ice or on land, and are not naturally aquatic creatures. Previous reports have noted individual animals swimming hundreds of miles to reach ice platforms or land, but this is one of the first to show these swims pose a greater risk to polar bear young.

"Climate change is pulling the sea ice out from under polar bears' feet, forcing some to swim longer distances to find food and habitat," said Geoff York of World Wildlife Fund, a co-author of the study.

York said this was the first time these long swims had been quantitatively measured, filling a gap in the historical background on this iconic Arctic species.

To gather data, researchers used satellites and tracked 68 polar bear females equipped with GPS collars over six years, from 2004 through 2009, to find occasions when these bears swam more than 30 miles at a time.

There were 50 long-distance swims over those six years, involving 20 polar bears, ranging in distance up to 426 miles and in duration up to 12.7 days, according to the scientific paper.

At the time the collars were put on, 11 of the polar bears that swam long distances had young cubs; five of those polar bear mothers lost their cubs during the swim, representing a 45 percent mortality rate, the study found. […]

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This seems like a strange addition to this piece. The Latin name for polar bears is Ursus maritimus, sea bear. This is not to deny that polar bears are likely toast within decades (if not outright extinction, then functional extinction combined with widespread local extinction) due to rapid changes to the Arctic ecosystem.